Browsing by Author "Lu, Haidong"

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Characterization of domain distributions by second harmonic generation in ferroelectrics
(2018-07-24)
Zhang, Yuan
;
Zhang, Yi
;
Guo, Quan
;
Zhong, Xiangli
;
Chu, Yinghao
Domain orientations and their volume ratios in ferroelectrics are recognized as a compelling topic recently for domain switching dynamics and domain stability in devices application. Here, an optimized second harmonic generation method has been explored for ferroelectric domain characterization. Combing a unique theoretical model with azimuth-polarization-dependent second harmonic generation response, the complex domain components and their distributions can be rigidly determined in ferroelectric thin films. Using the proposed model, the domain structures of rhombohedral BiFeO3 films with 71 degrees and 109 degrees domain wall, and, tetragonal BiFeO3, Pb( Zr0.2Ti0.8)O-3, and BaTiO3 ferroelectric thin films are analyzed and the corresponding polarization variants are determined. This work could provide a powerful and all-optical method to track and evaluate the evolution of ferroelectric domains in the ferroelectric-based devices.
Interface control of surface photochemical reactivity in ultrathin epitaxial ferroelectric films
(2013-05-06)
Chen, Jason
;
Lu, Haidong
;
Liu, Heng-Jui
;
Chu, Ying-Hao
;
Dunn, Steve
Asymmetrical electrical boundary conditions in (001)-oriented Pb(Zr0.2TiO0.8)O-3 (PZT) epitaxial ultrathin ferroelectric films are exploited to control surface photochemical reactivity determined by the sign of the surface polarization charge. It is shown that the preferential orientation of polarization in the as-grown PZT layer can be manipulated by choosing an appropriate type of bottom electrode material. PZT films deposited on the SrRuO3 electrodes exhibit preferential upward polarization (C+) whilst the same films grown on the (La, Sr)CoO3-electrodes are polarized downward (C-). Photochemical activity of the PZT surfaces with different surface polarization charges has been tested by studying deposition of silver nanoparticles from AgNO3 solution under UV irradiation. PZT surfaces with preferential C+ orientation possess a more active surface for metal reduction than their C- counterparts, evidenced by large differences in the concentration of deposited silver nanoparticles. This effect is attributed to band bending at the bottom interface which varies depending on the difference in work functions of PZT and electrode materials. (C) 2013 AIP Publishing LLC.